1. Technical Field
The present invention relates to an ink composition for ink jet recording.
2. Related Art
There has been known an ink jet recording apparatus for recording images and characters by ejecting fine droplets of an ink composition from a nozzle hole of a recording head to attach these fine droplets onto a recording medium. As an ink composition used in related recording, a water-based (aqueous) ink composition, in which a pigment, a pigment dispersant, a resin, and the like are dispersed or dissolved in water, has been known. Furthermore, a non-aqueous (oil-based) ink composition, in which a pigment, a pigment dispersant, resin, and the like are dispersed or dissolved in an organic solvent without containing water, has been developed.
Among the above ink compositions, a non-aqueous ink composition has been widely used because, in regard to a recording medium having a recording surface made of plastic (for example, vinyl chloride, polyester, polypropylene, polyethylene, or the like), the wet-spreading property of ink is good, or the fixing property of ink is good. For example, JP-A-2013-155275 discloses a non-aqueous ink composition for ink jet recording, containing an amide-based solvent (ether amides).
In addition, there is a case where a pigment dispersant, such as a resin dispersant, a pigment derivative (synergist), or the like, is added to a non-aqueous ink composition in order to improve the storage stability of ink by improving the dispersibility of pigment. For example, it is described in JP-A-2012-219131 that a pigment dispersed resin, a pigment derivative having a phthalocyanine skeleton, or the like is used.
The pigment derivative, as described in JPA-2012-219131, has a property of hardly dissolving in water, whereas has a property of easily dissolving in an organic solvent. Therefore, this pigment derivative tends to be separated from a pigment in ink, and tends to exist in a state of being eluted in a solvent. Particularly, when the amide-based solvent described in JP-A-2013-155275 is used, the pigment derivative is easily eluted in a solvent.
However, the amide-based solvent described in JP-A-2013-155275, compared to other organic solvents (for example, lactone, glycol ethers and the like), has an advantage of being excellent in the fixing property and the drying property of the recorded image, but has a property of high water absorption. Therefore, when a non-aqueous ink composition containing an amide-based solvent and a pigment derivative is stored for a long period of time, there occurs a problem that the pigment derivative eluted in a solvent hardly dissolves in the ink that comes to have a high water content, and thus this pigment derivative is precipitated as foreign matter. That is, foreign matter derived from the pigment derivative tends to be remarkably generated when the pigment derivative is used in combination with the amide-based solvent.
Thus, it was difficult to obtain an ink having excellent storage stability of the generation of foreign matter and the change of viscosity being lowered while improving the abrasion resistance (fixing property) of a recorded image.